They are translucent, with their faces, bodies and limbs strangely twisted and bent. They are usually bound to the place where they died.

Un-dead traits: immune to sleep, charm, and paralysis spells, as well as other mental effects and cold damage.

Life drain: all damage done gets added to their hit points (characters can regain lost hp normally).

Create spawn: any living humanoid killed by their life drain rises as a twisted ghost after the next sunset or after 1d4 rounds after “bleeding out” if it is currently night. “Recovering the body” is only possible before sunset and only if the respective ghost has been destroyed.

They are translucent, with their faces, bodies and limbs strangely tumid and bloated. They are usually bound to the place where they died.

Life drain: all damage done (both hp and STA loss) gets added to their hit points (characters can regain lost points normally).

Create spawn and un-dead traits: as above.

Adjusting for character level:

Both of these variants should be a good challenge for a party of 1st level adventurers if the number appearing is about half the number of characters. It will be a very difficult encounter if they don’t have magical or silver weapons (or clerics), so you might drop some hints or rumors so the players have a chance to prepare if they’re clever.

Silver weapons:

These are not readily available, but if there in a reasonably big city or market, a character may find a weapon suitable for them if they succeed on a luck check. The price should be about 30 times as much as the normal cost of the weapon.

A blacksmith might be willing to coat any weapon with silver for 20 times the normal price of the weapon; this is but temporary: after using such a weapon in a fight against a corporeal enemy, a luck check decides if the silver coating is still functional or wore out. Fighting incorporeal enemies does not tarnish the silver coating!

Magic weapons: These are never for sale. (Well, maybe if they are cursed.)